Different Options for Storage Tanks How To: Heating and Cooling with Storage Tanks
The prefer redranges of application of the heat transfer ﬂuids technology are given by the different organic heat transfer ﬂuids. The technical operation specialist book reference 'Heat Transfer Technique with Organic Fluids' describes plants that primarily use organic heat transfer ﬂuids. In this part of our PROCESS-Series we descripe how to construct Installations wherein production machines (e.g.presses) are heated and cooled with heat transfer oils.
Installations wherein production machines (e.g. presses) are heated and cooled with heat transfer oils can be constructed in different ways. The basic principle is that with all of these installations (hereafter referred to as the press) heat needs to be added to the consumer as well as removed during cooling. Therefore, a heater is required for heating the press and a cooler where the energy is removed again.
Simple Design of Heater/Cooler (I)
The simplest way to solve the problem is to merely provide a heater and a cooler. During heating, the thermal oil initially ﬂows through the heater; there, it is heated and then ﬂows into the press, where it dissipates heat, and then back to the heater. This heating is applied as long as required until the relevant temperature is reached in the press. For the cooling process, the heater is switched off and the thermal oil is no longer routed through the heater, but instead through a cooler (water- or aircooler), where it is cooled. These installations are simple in design and are still built to day for smaller thermal power requirements. The disadvantage is that relatively large heater and cooler powers are required, because the heating and cooling is often only required within short periods.
Design of Heater with Hot Oil Storage/Cooler (II)
The disadvantage of increased heater power mentioned under (I) arises because of the need to switch off the heater during the cooling process. If it were possible to allow the heater to also continue to operate during the cooling process, it would be possible to have a smaller heater for a speciﬁc installation power (option for heat storage -accumulation).This leads to the possibility of using a hot oil store so that the heater operates continuously. During the cooling process, the heater heats up the thermal oil in an accumulator. This installation has a hot oil store but no cold oil store, because costs per installed kWh for the heater circuit are considerably higher than costs per installed kWh for the cooler circuit. Thus, by introducing the hot oil store, installations (II) become more cost-effective than installation (I) which functions without a store.
Design with Heater/Hot Oil Storage – Cooler/Cold Oil Store (III)
The logical next step in the development of these plants is the application of both hot and cold oil storage. The cold oil store becomes particularly useful with the application of air coolers, because air coolers have higher investment costs than water coolers, which are relatively inexpensive. In addition, the overall economics of the process improve slightly if two stores are used. This is because, by using a suitable arrangement of the valves, part of the heating or cooling energy can be recovered, which is not possible with the level (I) installation. (There,when switching over from heating to cooling, the hot ﬂuid, for example 200 °C, must be admitted to the cooler, thereby expunging the total energy. If stores are used, part of this energy can be recovered.)
Design of a Heater/Cooler with Hot Oil/Cold Oil and Compensation Tank (IV)
Efforts have been made to further improve the heat recovery during heating and cooling, particularly for large installations. This has led to the application of a third store as a compensation tank.